br can not backup and resotore tidb system databases like mysql.user

[wangbincmsss]

Question

i want to backup and restore all tidb data , but br can not backup and resotore tidb system databases
and i see this in code

br can not backup and restore tidb system databases like mysql.user
i want to know the reason ?

[wangbincmsss]

\cc @kennytm

[kennytm]

@wangbinhe3db we explicitly opt out of system tables. Because if the user wrongly restore on a cluster with different schema version, BR can easily brick the entire cluster. See #679 for the intended direction how we'd like to handle system tables.

[SunRunAway]

1. mysql.user may have the account information which customer may forget in their brain.
2. TiDB allow a customer to create a table in the mysql schema.

I suggest we should backup the system tables, and can opt out when restoring.

@kennytm @IANTHEREAL

[SunRunAway]

The second reason is very important and critical.

As a matter of principle, we should also back up everything and restore selectively, instead of backuping selectively.

[kennytm]

@SunRunAway please discuss the plan about system tables in #679. i'm closing this issue as duplicate.